1970 LT1 valve spring recommendations

[Steven S.]

I'm looking for any suggestions/recommendations on a valve spring for a stock 70 LT1 build. I imagine everyone has a version of this spring, but I'm sure all are not created equal. Seems to be some knowledgeable LT1 guys here, so hopefully you will chime in.

Thanks,
Steve

[Duke W.]

Re: 1970 LT1 valve spring recommendations

The LT-1 of that era used the same valve spring as your grandmother's 283-2 bbl. - 3911068. An exact duplicate is Sealed Power VS677, which can be found on the Web for about 20 bucks a set. With careful setup of installed height to allow .090-.100" coil bind clearance they are good to about 7200 with the OE-design cam, and if you massage the heads, it will make useable power to about 7000.

Duke

[Steven S.]

Re: 1970 LT1 valve spring recommendations

Thank you for the info!

[Paul D.]

Re: 1970 LT1 valve spring recommendations

I often see Duke say "Massage the Heads"....What is he refering to?.....Port/polish....Bowl work.....3 angle valve job/bigger valves......what type work on the heads involved?.....PD

[Duke W.]

Re: 1970 LT1 valve spring recommendations

Pocket porting, port matching, chamber relieving (to eliminate head chamber bore overhang, which is especially important on the exhaust side), and three angle valve seats with a relief cut off the top of the valves to eliminate the unused portion of the valve seating surface. No polishing! That's just cosmetic, and a waste of time and effort or money if you have the work done by a professional.

Little material actually needs to be removed, so the port volumes only increase by a few cc. Don't confuse this with "race porting" where the heads are ported all the way through. The purpose of "head massaging" is to improve the port flow coefficients so they are less restrictive at high revs, and if done correctly with all other OE components for any OE configuration, top end power will improve by about ten percent and the useable rev range will increase by 500 to 1000 revs. You not only get more peak power, but you get a wider range where the engine produces at least 90 percent of peak power. The SOTP difference is dramatic, but the engine will appear just like original and retain the original idle characteristics and normal operating behavior.

See the Fall 2010 Corvette Restorer "...Tale of Two Camshafts" article for more info including flow tests, and the details are in the Chevrolet Power Manuals from the seventies and HP Book's "How to Hot Rod Small Block Chevys".

Duke

[Patrick H.]

Re: 1970 LT1 valve spring recommendations

and the details are in the Chevrolet Power Manuals from the seventies

Duke

Duke,

Any idea which edition of the Chevrolet Power Manual?

Patrick

[Duke W.]

Re: 1970 LT1 valve spring recommendations

I think I have the second, third, and fifth additions, and I believe all of them have drawings on how to modify heads. They specifically refer to the OTC heads designed for "off road use", but the same basic techniques apply to production heads. The newer additions added information on race preping the V-6 and Cosworth Vega engines.

Some of these same drawings are also in "How to Hot Rod Small Block Chevys", which also has a very good drawing of how to do a three angle valve job.

Duke